Medroxyprogesterone acetate (MPA; 5 micrograms/g body wt) or norethisterone oenanthate (NET-OEN; 4 micrograms/g body wt) was given to lactating female rats by subcutaneous injection 1 day after parturition. Each female suckled ten female pups which had been randomly allocated to her and at 21 days of age the pups were weaned. In this way female pups were exposed to either MPA or NET-OEN via milk during suckling. The patterns of LH and progesterone secretion at pro-oestrus were investigated using radioimmunoassay. When these pups reached adulthood it was found that neonatal exposure to MPA via milk significantly reduced the pro-oestrous LH peak by 45% as well as the total amount (by 27%) of LH secreted during pro-oestrus. Neonatal exposure via milk to NET-OEN had no effect on LH secretion during pro-oestrus. Pro-oestrous progesterone secretion was unaffected by either MPA or NET-OEN treatment.

Medroxyprogesterone acetate (MPA), 5 micrograms/g body wt, was given to lactating female rats 1 day after parturition. Group 1 females suckled 10-12 young, with equal numbers of males and females, while Group 2 females each suckled 10 female young. The young were weaned at 21 days of age. Exposure to MPA advanced the day of vaginal opening by 1 day, and increased anogenital distance in Group 2 young. At autopsy between 80 and 100 days of age, the clitoris of Group 2 females was significantly greater than in controls, and ovarian and adrenal weights were reduced.